1. Field of the Invention
The present invention relates to a titanium nitride-stripping liquid, and a method for stripping a titanium nitride coating film.
2. Related Art
Conventionally, etching processing in manufacture of semiconductor devices and the like generally includes: coating a resist material such as a photoresist or an electron beam resist on the surface of a substrate to be etched; carrying out etching using as an etching mask the resist film formed to have a pattern by a lithography technology; stripping the resist film after the etching; and thereby forming a specified pattern on the etched substrate. According to such a process, in etching with the resist film as an etching mask, there may be a case in which the resist film does not sufficiently serve as the etching mask, depending on the etching rate of the used substrate to be etched due to the problems of etching selectivity of the resist film for the substrate to be etched.
Therefore, when a substrate to be etched which may have lowered etching selectivity is etched using a resist film as an etching mask, high etching selectivity of the etching mask for the substrate to be etched is maintained by providing an etching mask referred to as a hard mask constituted with a titanium coating film, a titanium nitride coating film or the like. A stripping liquid of an etching mask has been desired, which can remove the etching mask constituted with titanium or titanium nitride after etching the substrate to be etched without causing damage on a conductor layer or an insulating layer, in the case of use of the hard mask as an etching mask.
Known other technologies in which a titanium nitride coating film is used include, for example, techniques for producing a transistor having a hybrid gate structure. In p type transistors having a hybrid gate structure, a structure is formed in which a titanium nitride coating film is laminated on a high-permittivity film. As an etching liquid that is a titanium nitride-stripping liquid used in pattern formation of this titanium nitride coating film, an etching liquid has been desired which does not affect characteristics of the high-permittivity film.
As a liquid for dissolving the titanium thin film, Japanese Unexamined Patent Application Publication No. 2002-146562 discloses an etching agent of titanium which includes an aqueous solution containing hydrofluoric acid and hydrogen peroxide. According to the etching agent of titanium disclosed in Japanese Unexamined Patent Application Publication No. 2002-146562, fine pattern formation of a titanium thin film is reportedly enabled without corrosion of the resist, and with less influences on the substrate material such as aluminum or an alloy thereof, SiO2, or Si.